Exploring the systematic uncertainties of SNe Ia

Shuang Wang

Northeastern University

Outline

• 1. Introduction

• 2. Previous Works

• 3. Current Works

• 4. Summary

Introduction

systematic uncertainties of SNe Ia

• errors in photometry, calibration and identification of SNe Ia

• host-galaxy extinction

• gravitational lensing

• intrinsic variation of physical properties of SNe Ia

Lightcurve fitter modelChi^2 Statistics

Supernova Training(Using all SNe)

Light-curve FittingFor one SN

cosmology Information

(μ, α, β)

Light-curve Fitting

• 1) rest-frame model mags + k-corrections: Mlcs2k2 (Jha,Riess,Kirshner ApJ 659 122 2007)

• 2) rest-frame spectral model: SALT2 (Guy et. al., A&A 466,11,2007)

stretch-luminosity parameter

color-luminosity parameter

ApJS 192, 1 (2011)

Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey

A. Conley et. al.

The possible evolution of α and β

• For the Pan-STARRS1 data Scolnic et. al., arXiv:1310.3824

• For the Union2.1 data Mohlabeng and Ralston, MNRAS 439, L16 (2014)

Shuang Wang, and Yun Wang

Phys. Rev. D 88, 043511 (2013)

Exploring the Systematic Uncertainties of Type Ia Supernovae as Cosmological Probes

Previous Works

For the SNLS3 data

Current Works

Phys. Rev. D 89, 063524 (2014)

Exploring the evolution of color-luminosity parameter β and its effects on parameter estimation

Shuang Wang, Yun-He Li, and Xin Zhang

ΛCDM model, wCDM model, CPL model

Fitting Results

Shuang Wang, Jia-Jia Geng, Yi-Liang Hu, and Xin Zhang

arXiv:1312.0184

Revisit of SNLS3 constraints on holographic dark energy: the effects of varying β and different light-curve fitters

Summary

• For all the models, adding a parameter of β can reduce the best-fit values of chi^2 by 36

• β deviates from a constant at 6σ CL• A time-varying β has significant effect on param

eter estimation• Considering the evolution of β is very helpful for

reducing the tension between supernova and other observations

• Open questions: other systematic uncertainties? How to deal with them?